"Taro Alien" is a science-fiction anime series centered around a young boy named Taro, who discovers he is not entirely human. Taro's life takes a dramatic turn when he learns he is the result of an experiment conducted by an alien race. These extraterrestrial beings, known as the Zorians, created Taro by combining human DNA with their own advanced genetic material, intending for him to serve as a bridge between their species and humanity. However, the experiment was abandoned, leaving Taro to grow up unaware of his origins.

The narrative unfolds as Taro begins to exhibit unusual abilities, such as enhanced strength, telekinesis, and the capacity to communicate with alien technology. These powers attract the attention of both the Zorians, who now seek to reclaim him, and a secretive Earth-based organization determined to study and control him. Taro is thrust into a conflict that forces him to confront his identity and the ethical implications of his existence.

Key characters include Taro's adoptive parents, who provide emotional grounding and moral support as he navigates his dual identity. A Zorian scientist named Lira, who initially views Taro as a mere experiment, gradually develops a protective bond with him, challenging her own species' cold logic. On the human side, Dr. Akane, a researcher working for the shadowy organization, becomes a pivotal figure as she grapples with her conscience while pursuing Taro for study.

The series explores themes of identity, belonging, and the ethical dilemmas surrounding genetic experimentation. Taro's journey is marked by his struggle to reconcile his human emotions with his alien heritage, as well as his efforts to forge a path that neither fully aligns with the Zorians' ambitions nor the humans' fear-driven agendas. The plot is driven by a mix of action, introspection, and moral quandaries, culminating in a resolution that underscores the complexity of coexistence between vastly different species.